1. Field of the Invention
This invention relates to novel pesticide and fungicide compositions obtained from neem seed extracts prepared by extracting seeds with non-polar hydrophobic solvents. More specifically, a neem wax and a clarified neem oil fraction are prepared which exhibit the consistent ability to repel pests from plant surfaces and to kill pests and fungi at various life stages.
2. Description of Prior Art
The neem tree, a tropical evergreen, has been used for centuries as a source of insecticides to which insects have not developed a resistance. Various neem seed extracts, particularly the ones containing the tetranortriterpenoid azadirachtin, are known to influence the feeding behavior, metamorphosis (insect growth regulating effect), fecundity, and fitness of numerous insect and fungal species belonging to various orders.
Neem seeds also contain an oil substance which has been used for its medicinal and therapeutic properties for centuries. However, "neem oil" has been produced by a number of methods and this has lead to a great variability in the properties of materials designated as "neem oil". Very little chemical characterization has therefore been possible. Many of the publications referring to "neem oil" give no information as to its preparation, which is the key determinant of its composition.
There are two principle methods of removal of oil from neem seeds: expulsion, where the oil is pressed from the seeds, and extraction, where the oil is removed from the seeds by solubilization in a solvent. Inherently, materials made by these methods have very different properties. Oil expelled from the seed will also contain water expelled from the seed by the same process. This aqueous material will carry along with it liminoids, such as azadirachtin, which themselves have insecticidal activity.
Khan et al. (1986) report that neem oil (source unidentified) showed no inhibitory affect on the growth of a variety of fungi. In fact, it is reported that the neem oil was contaminated with molds including Aspergillus niger and Aspergillus flavus. Similarly, Sharma et al. (1986) report that 3-5% neem seed oils (no method of preparation given) had no effect on the control of pod borer Heliothis armigera on chick-pea, and Gujar et al. (1985) report that neem seed oil (no method of preparation given) had no effect on the desert locust, Schistocerca gregaria.
Contrary to this, it has been reported that neem oil formulations prepared by expressing oil from the seeds or by extracting with aqueous solvents are effective insecticides and fungicides. It is reported that 10% neem oil (preparation unidentified) (Anon. 1986) inhibited the growth of certain fungi in vitro. Dreyer (1986) discloses that neem oil obtained by handpressing in the cold was similar in the control of phytophagous arthropods to aqueous extracts; expeller-pressed oil was much less active. Singh et al. (1980) reports that neem oil obtained with a Soxhlet apparatus, no solvent given, controls fungi including Fusarium oxysporum, Rhizoctonia solani, Sclerotium rolfsii and Sclerotia sclerotiorum. It is likely that all of these materials contained appreciable polar moieties, including several liminoids.
Similarly, neem oil has been reported to have insecticidal properties but the reports of efficacy are often in conflict, perhaps because of significant differences in the composition of the "neem oil" tested. Furinstau et al. (1985) report that a 1% suspension of neem oil (no method of preparation identified) is effective at controlling aphids but is phytotoxic to sorghum plants. Yet Saxena et al. (1984) report that a &gt;6% suspension of neem oil is necessary to achieve statistical control of the plant hopper Nilaparatu lugens on rice seedlings, apparently with no phytotoxic effect.
Hydrophobic solvent extracted neem oil is disclosed in U.S. Ser. No. 07/456,762, now abandoned (Locke et al.). It is taught that the disclosed formulations exhibit the ability to repel insects from plant surfaces, prevent fungal growth and kill insect and fungal pests at various life stages.
It has now been discovered that consistent fungicidal and insecticidal neem fractions can be obtained from hydrophobic solvent extracted neem oil by fractionating the neem oil by cooling to obtain a neem wax fraction and a clarified neem oil fraction. Furthermore, it is shown that freeze fractionation of the neem oil produces a lower-phytotoxic clarified neem oil material.